1. Field of the Invention
The present invention relates to an electric power system protection and control system in combination of digital protection controllers, such as digital relays, to protect and control an electric power system by inputting status quantities of the electric power system and converting them into digital data and a display controller to display and control the monitoring of operation and status of the digital protection controllers via a communication network, and a distributed control system.
2. Description of the Related Art
Digital protection controllers, such as digital relays, are already used widely in the field of the electric power system, and are made highly functional by use of highly efficient microprocessors and memories of large capacity, etc. in recent years. In particular, for the labor saving of their operation and maintenance, it becomes possible to realize a remote operation and monitoring system for operating and monitoring the operation and status of digital protection controllers via a wide area transmission network from a long distance.
In these systems, it is possible to display electrical quantities (current and voltage quantities converted into digital data) input from an electric power system at a distant place via a transmission system in addition to the detailed information relative to the operation and status of digital protection controllers. Definite examples of these systems are disclosed in literatures, for instance, (The 1996 National Meeting of The Institute of Electrical Engineers of Japan, Lectured Theses 1529 "Development of Digital Relay Remote Operation Monitoring System").
On a system for the purpose of the remote operation of conventional digital protection controllers, such as digital relays, it takes such a form that along the remote operation menu of digital protection controllers (hereinafter referred to as "Protection Controllers"), a request is submitted from a remote personal computer via a wide area transmission network. When this request is received, the protection controller performs the process according to the request and returns a response to the personal computer that sent the request. An example of the remote operation menu is shown in FIG. 40.
A case in taken to change the setting, for example, the setting of a threshold value of the relay operation in a digital relay, according to a setting menu as an example. As shown in FIG. 41, the steps will be as shown below: First, selecting a display control menu after selecting a substation and equipment and connecting the communication according to a communication menu within a remote operation menu; and then, after further selecting the setting, setting elements to be changed are selected, numerical values to be changed are input and a writing request is submitted to EEPROMs in the protection controller, and thereafter, an operation starting request is submitted.
In this case, until a series of processings is completed, it is necessary to maintain the connection between the personal computer and the protection controllers. Accordingly, there will be a first problem that delay of communication accompanied with increase in the traffic on a communication network and drop of reliability generated from loss of communication packets.
FIG. 41 shows the change of one setting element. But so as to change plural setting elements, a required time further increases. Further, to have a personal computer generate various requests corresponding to the above-described remote operation menu, it is required for the operator to operate the personal computer to each request.
This means that when functions of a protection controller become complicated and versatiled, the number of operations increase and workload of the operator increases. Further, when plural protection controllers are required to execute the same operation, it becomes complicated as the same work is performed for different controllers, and there will be caused such a second problem that with the increase of workload, the drop of reliability due to human error will be generated.
Further, in case of such a remote operation system, plural protection controllers are operated by a single personal computer. In this case, it will become necessary to configure the system by taking differences in the substances of protection controllers (for instance, setting elements due to different protection relaying scheme) into consideration.
The configuration in this case is shown in FIG. 42. As shown in this FIG. 42, the configuration at the personal computer side is corresponding to the kinds of protection controllers. This means that with the increase in kinds of protection controllers, the volume of the corresponding software that is to be provided on a personal computer increases, and there will be such a third problem that the necessity for modification is produced and the economy and reliability of the system will become worse.
Further, in such a remote operation system, as a local network and a wide area transmission network are used, the protection controllers can be easily operated remotely at a place where they can be connected to these communication networks. In other words, the remote operation can be made similarly through personal computers installed at plural locations.
This state is shown in FIG. 43. In this case, it is necessary to provide a remote operation software that is corresponding to each protection controller to each personal computer as described above, and there will be a fourth problem that this system is inferior in the aspect of economy such as required expenses and maintenance.
Further, as it becomes possible to monitor the operation of plural protection controllers by a single personal computer in the remote operation system as described above, it is possible to compare related same items (for instance, electrical quantities of the system taken by plural protection controllers connected to the same system).
In this case, a personal computer is connected to protection controllers subject for communication and displays operating items along the remote operation menu shown in FIG. 40. If it is desired to check the state of the same items on other related controllers, a personal computer is connected similarly to the related controllers for communication and displays the items along the operation menu shown in FIG. 40.
In this case, if the number of protection controllers subject for control is increased, such operations as selection of controllers, connection for communication and selection of items become necessary for each protection controller and the operations becomes very complicated, and related other protection controllers and items are displayed independently for each protection controller. However, as they are not displayed as related protection controllers and items in the same picture, there will be such a fifth problem that the comparison of related items will become an overload for operator.
In this case, it is considered to consolidate the menu for every same related items over plural controllers. But if it is required to see different items for each controller, it will be complicated conversely, and in addition, the maintainability will become a problem when there is an increase/modification of the controller. Further, there will be such a sixth problem that if the same protection controller is accessed simultaneously by plural display controllers, the processing load of the protection controller increases in order to respond to the access and therefore, a response is delayed.
Further, for such a remote operation system there is the possibility for demand to realize versatile functions. For instance, conventionally the protection, control and measurement of an electric power system are separated as separate controller. It is considered to consolidate these functions in the same controller. In this case, there will be a seventh problem that the processes to be incorporated in a protection controller increase and an excessive load is generated in the aspect of the economical efficiency, reliability and maintainability.
Further, when changing the specification of a protection controller, it is a general practice to stop the controller and change a ROM containing a program, and there will be an eighth problem that the drop of availability of the system and complicated changed workload.
Digital protection controllers are already used widely in the field of the electric power system, and are made highly functional by use of highly efficient microprocessors and memories of large capacity, etc. in recent years.
Definitely, there are a digital relay to judge system faults, a fault locator, a failure extension protection equipment, etc. The digital protection controllers described above are widely used in the operation of electric power systems at present.
Hereinafter, taking a digital relay as an example, a conventional technique will be described. FIG. 44 shows the construction of a basic digital relay. The digital relay is composed of an analog-to-digital conversion unit 10-1, a digital processor 10-2, an input/output interface 10-3 with such external equipment as a breaker, etc. and a bus 10-5. Further these units 10-1 through 10-3 are connected each other via bus 10-5.
Analog-to-digital conversion unit 10-1 is composed of analog filters 1-11 to 1-1n , sampling hold circuits 1-21 to 1-2n , a multiplexer 1-3 and an analog-to-digital converter 1-4. It takes status quantities of an electric power system that is an object of protection and control as n-pieces analog information A-1 to A-n and converts them into digital quantities after having held at a specified sampling interval.
On the other hand, digital processor 10-2 is composed of a CPU 2-1, a RAM 2-2, a ROM 2-3 and a non-volatile memory EEPROM 2-4. The data of electrical quantities converted to digital data described above are transferred to RAM 2-2 successively, and according to this data, setting values of the protective relay stored in EEPROM 2-4 and programs from ROM 2-3, CPU 2-1 performs various protection and control operations such as calculation relaying program.
Next, input/output interface 10-3 is an interface to perform by taking the state of external control equipment such as information on a circuit breaker, to output the operation of the protective relay, reset output, trip command, etc. to external equipment. A definite example of the construction of the digital relay is as described above.
In case of the digital relay, its principal duty is to protect an electric power system. The result of the proper protection by the digital relay is stored in RAM 2-2 as data (the operating state of the relay, electrical quantity, other related information) at the time when a trip command is output to a circuit breaker from input/output interface 10-3, and generally confirmed by operator by reading these data.
On the other hand, for labor saving in the operation and maintenance of digital protection controllers such as digital relays, it becomes possible to realize a remote operation monitoring system to monitor the operation and status of digital protection controllers remotely via a wide area transmission network in recent years. In this system, digital electrical quantities (current, voltage converted to digital data) input through an electric power system can be displayed at a remote location via a transmission system in addition to detailed information on the operation and state of digital protection controllers.
A definite example of this system is disclosed in literatures, for instance, (The 1996 National Meeting of The Institute of Electrical Engineers of Japan, Lectured Theses 1529 "Development of Digital Relay Remote Operation Monitoring System"). Examples of menu items that are usable in the remote operation monitoring system are shown in FIG. 40.
As shown in this FIG. 40, items required for the operation monitoring of the digital relay are all usable at a remote location. When this remote operation monitoring system is applied, it becomes now possible to display and check the result of the operation of such protection controllers as the digital relay on a display controller, such as a personal computer, in a remote attendance substation.
It the present digital relay and remote operation monitoring system to monitor the operation of the digital relay, if a system fault occurs as described above, the contents of operation accumulated in the operated digital relay (operated relay element, electrical quantity and other related information) are read out and checked at a remote location.
So far, if a system fault occurs and one of digital relays installed at various locations is operated, in order to check if the relay operated properly, an operator goes to the location where that digital relay is installed and checks the contents of the operation. In particular, when it is estimated that the relay has not operated properly, it is necessary to check the contents of the operation of corresponding digital relay (including a controller not in operation) more in detail and much labor is needed.
As it becomes no longer required to go to a substation where a digital relay is installed if the remote operation monitoring system described is applied, labor required for the checking work when the controller is operated decreases. However, there are such problems as described below.
First, the present remote operation monitoring system has item menus for every controller as shown in FIG. 40. When operator checks the contents of the operation of a controller as shown above, out of the menu of operations, for instance, on the "Relay Operation" screen, the relay operation when the controller is operating is checked to judge whether the proper relay element operated or an unnecessary relay element operated. On the "Electrical Quantity" screen, in what size and phase the system electrical quantity was when the controller operated, and the validity with the operating and non-operating state of relay element is judged. Further, on the "Related Information" screen, the input state of the controller when it was operating (for instance, a circuit breaker) and the state of the transmission system is checked and correlated with the relay operation.
Thus, the state of an objective controller is checked through many steps. In this case, data requested from a personal computer and response data from a digital relay go back and forth alternately as shown in FIG. 45, and the communication route between the personal computer and the digital relay must be kept maintained for a long hour until a series of processes are completed. As a result, there is such a first problem that reliability may drop due to increase in the traffic on the communication network and delay of communication and lost of communication packets resulting therefrom.
Further, in such the analyzing work when the controller is operated as described above, it is also required to collect the contents of operations of plural digital relays related to the system fault and compare them. By the comparison, normality or abnormality of the controller operation can be known. For instance, if a system fault occurred in one of two parallel transmission lines, it becomes possible to judge whether the controllers were operated normally or not operated by checking and comparing the operational contents of at least 4 controllers protecting both ends and respective lines of two transmission lines.
However, in case of the remote operation monitoring system described above, as the connection of communication with an objective controller and the selection of the screens corresponding to menu items are needed for each controller and their operation becomes very complicated. Furthermore, although the display screen of related other controllers and items are displayed independently for each controller, they are not displayed as related controllers and items in the same screen, there is a second problem that operator is excessively burdened when the operator compares related items.
In this case, it may be considered that the menus for plural controllers may be consolidated by the related same item. However, when it is desired to see different items for each controller, it becomes complicated inversely, and further, the maintainability will become a problem when controllers are increased or modified. The more system faults are taken place in a wide range and are complicated, the more these problems come out remarkably.
Further, the system fault types are generally always different. For instance, controllers that are operated change, whenever a fault occurs, depending on component elements composing an electric power system, such as transmission line, bus, transformer, etc. and fault occurring place. In other words, operator must judge which digital relay should be checked for the contents of operation, whenever a system fault occurs, according to its fault aspect and perform the required work accordingly. Thus, there is a third problem that this will make the work complicated, and further, controllers that must be checked may be missed or conversely, controllers that are not required for the checking are checked.
Further, there is a fourth problem as follows. In order to check the validity of the operation or non-operation of controllers when a system fault occurs, it is necessary for operator to know a general aspect of the fault (for instance, a single line earth fault, two line short-circuit fault, etc.) from voltage and current waveforms at the time of system fault obtained from an electric power system observation unit such as an oscillograph equipment, etc. installed independently from the digital relay. It is further necessary for operator to make the overall analysis and judgment from the general aspect of the fault, the contents of operation of the digital relays and the state of the system. Thus, much labor of operation is needed and operator may make a miss judgment depending on his ability.
As a characteristic of a digital relay, there is an automatic supervising function. The automatic supervising function is a monitoring function incorporated in the relay unit so that the system protection function, that is an obligation of a digital relay will work normally. Detailed contents are described, for instance, in the "Practical Reader for Digital Relay", p. 70 through 73, etc. edited and written by Izumi MITANI, published by Ohm Corporation.
In this respect, the automatic supervising described in this literature is roughly divided into the continuous monitoring and automatic checking. In the continuous monitoring, the monitoring function works at the periodical fixed cycle. The automatic checking is to confirm its operation by starting the output circuit process, etc. that does not regularly work, at predetermined intervals (for example, once a week), as well to detect the failure to operate mode.
By such an automatic supervising function, a failure of digital relays has been quickly detected. As a result, a probability to produce a non-correct operation like a failure to operate at occurrence of an electric power system fault or an unwanted operation at a fault of out of the zone is lowered. From the above-mentioned background, accompanied by the diffusion of digital relays, the importance of an automatic supervising function has been increased.
On the other hand, for labor saving in the operation and maintenance of digital protection controllers such as digital relays, it becomes possible to realize a remote operation monitoring system to monitor the operation and status of digital protection controllers remotely via a wide area transmission network in recent years. In this system, digital electrical quantities (current, voltage converted to digital data) input through an electric power system can be displayed at a remote location via a transmission system in addition to detailed information on the operation and state of digital protection controllers.
A definite example of this system is disclosed in literatures, for instance, (The 1996 National Meeting of The Institute of Electrical Engineers of Japan, Lectured Theses 1529 "Development of Digital Relay Remote Operation Monitoring System"). Examples of menu items that are usable in the remote operation monitoring system are shown in FIG. 40.
As shown in this FIG. 40, items required for the operation monitoring of the digital relay are all usable at a remote location. When this remote operation monitoring system is applied, it becomes now possible to display and check the result of the automatic supervising carried out in the digital relay on a display controller, such as a personal computer, in a remote office.
In the present digital relay and remote operation monitoring system to monitor the operation of the digital relay, the automatic supervising is carried out in individual digital relays as described above, resulting in the state that its result can be remotely confirmed.
On the one hand, in the operation and maintenance of digital type protection controllers including digital relays, the work called as a patrol has been carried out from conventionally. This is a work to individually confirm the status of digital relays installed in substations, etc. For instance, they are confirmed from the viewpoints of whether there is any relay element in the operating state, whether the automatic checking is conducted at precise cycle, whether there is other defective display, and whether there is any difference in the states of a adjourning plurality of controllers, etc. Besides, in case a failure occurrence or an omen of failure occurrence is recognized, the action to restore (for example, replacing the hardware, remodeling the software or changing the relay set value) is taken.
This has been carried out to confirm the result of the above automatic supervising function. To supplement this, it has been carried out to discover the mode of the failure which can not be found by the automatic supervising (for example, failure of automatic supervising function itself or partial failure that cannot be detected in the automatic supervising function).
Since such a work for a patrol like this is carried out by the work that operators go to a remote unmanned substation, and by confirming the display state and operating state of each digital relay judge and record, a large workload comes to be required. In the above remote operation monitoring system, due to the fact that operators do not go remotely, but the display of digital relays can be confirmed, it is possible to substitute a part of the work for a patrol by such system. However, there are problems as described below.
First of all, there is each item menu per each controller as shown in FIG. 40 in the present remote operation monitoring system. In case that the work corresponding to the work for a patrol as described above is carried out, for instance: the automatic checking executing number is confirmed in the "Automatic checking" picture, it is judged whether it is the correct number; it is judged whether the system electrical quantity is fetched as a correct value in the "Input electrical quantity" screen: it is confirmed whether each relay element operates unnecessary in the "Relay Operation" screen; and it is confirmed whether a failure is not detected by the automatic supervising in the "Abnormal contents" screen.
The state of the controller in object is confirmed by many procedures like this. In this case, it is necessary that the communication route between the personal computer and the digital relay is kept for a long time until a series of processing will end as shown in FIG. 46. There is a first problem that the increase in the traffic on the communication network and the lowering in reliability by the delay in communication and the loss of communication packets resulting therefrom.
Furthermore, a plurality of controllers are compared in the work for a patrol as described above, there is an advantage that an abnormality of a controller is aware relatively early. For instance, in case of two digital relays for protection of transmission line to receive electrical quantities from the same transmission line, the input electrical quantities fetched to the controllers are the same. The fact that these two quantities are different can be judged as a failure of the analog-digital conversion unit in FIG. 44 or an omen that it reaches to the failure.
Further, the automatic checking executing numbers are the same in 2 controllers whose automatic checking cycles are the same and which begin their operation at the same time. The fact that these numbers are different can be judged that there is any abnormality in the processing related to the automatic checking. There are many advantages to perform the comparison of states of a plurality of controllers.
However, in case of the remote operation monitoring system described above, as the connection of communication with an objective controller and the selection of the items are needed for each controller and their operation becomes very complicated. Furthermore, although the display screen of related other controllers and items are displayed independently for each controller, they are not displayed as related controllers and items in the same screen, there is a second problem that operator is excessively burdened when the operator compares related items.
It this case, it may be considered that the menus for plural controllers may be consolidated by the related same item. However, when it is desired to see different items for each controller, it becomes complicated inversely, and further, the maintainability will become a problem when controllers are increased or modified.
Further in recent years, there is a trend that functions to store in digital type protection controller are increased, and thereby protection controllers become complicated. An automatic supervising function including a diagnostic function for specifying a fault part increases accompanied by this. Consequently, there is a third problem in economical efficiency that the quantity of automatic supervising software in the protection controller comes to be large, and memories required come to be large.
Further, in case a change in the monitoring function is produced by the change in the operation of a controller (change in input quantity, addition of relay element, etc.), or in a case that a change is produced by the functional improvement, in the conventional system, it is required to change the contents of the ROM to store the program to realize a monitoring function and a diagnostic function. For this reason, there is a fourth problem that the controller is stopped and the availability thereof decreases.
Further, there is a fifth problem that a great time is required, in the present situation, in the work that a failure part is supposed and restored after the abnormal state of a controller is found by an operator through a patrol, and in the judgment that a time for a round of next inspection is determined from the history of the working results in the past, etc.
In the conventional remote operation monitoring system to operate and monitor from far away a protection controller like a digital relay, the protection controller is operated by the menu shown in FIG. 40. The setting work to perform by the "Setting" menu in this menu is an important work to determine a sensitivity and a characteristic of the protection and control function, and it is necessary to set without errors all the setting values of relay elements which a protection controller has.
In recent years, as the high functionality and multi functionality of protection controllers, the number of relay elements to be stored in a protection controller is in a trend of increase. Accompanied with this, the number of setting elements has been also increased. However, the change and/or confirmation method of setting values have been as conventional, and this state is shown in FIG. 47. FIG. 47 shows the data exchange between the display controller and the digital relay in case setting is performed from the remote display controller by the remote operation monitoring system.
First, a display control menu is selected after selecting a substation and equipment according to a communication menu within a remote operation menu and the communication line is connected. Then, after further selecting the setting, a setting element to be changed is selected, a numerical value to be changed is input and a writing request is submitted to an EEPROM in a protection controller, and thereafter, an operation starting request is submitted.
The above is described about the change of one setting element. In case of the change of plural setting elements, the above procedure is to be repeatedly made by the number of elements. Further, at this time, in case a state like abnormality of hardware in the controller or an operation of a relay, etc. is produced, since performing the change in setting is apt to lead to an unwanted operation of a controller, it is generally suspended. In this case, it is necessary to perform the confirmation by the other menu item in FIG. 40, and this also increases the workload.
The above is also similar in the case in which the setting work is performed by the panel for setting, etc. on the front of the digital relay without using a network. Thereupon, the setting work causes an increase in the workload and a human error accompanied with this, and there will be a first problem to drop both economical efficiency and reliability.
Further, the setting for controllers in subject is performed by many procedures like this. In case a remote operation system is used, as shown in FIG. 47, a request data from a personal computer and a response data from a digital relay mutually come and go. It is necessary to maintain a communication route between the personal computer and the digital relay until a series of processing is completed. Accordingly, there will be a second problem that a drop of reliability is generated, because of increase in traffic on the communication network, and delay of communication and loss of communication packets, etc. accompanied with it.
Further, in many cases the change in setting accompanies the change in condition of the electric power system in subject. In this case, the similar change in setting values is to be performed over plural protection controllers. But there will be a third problem that economical efficiency and reliability is lowered by repeating the setting change procedure as described above similarly against each controller.
Moreover, in case considering that setting values are changed in response to the change in the electric power system as described above, since the workload is much as described above there is a predetermined limit in the following time. The larger the range of the subject system is, the larger this delay becomes. Accordingly, there will be a fourth problem that the protection and control of the electric power system cannot stably performed.